Fuel cell stack having an improved pressure plate and current collector

• US 6,764,786 B2
• Filed: 05/08/2002
• Issued: 07/20/2004
• Est. Priority Date: 05/08/2002
• Status: Expired due to Term

• Current Assignee: Audi AG (Volkswagen AG)
• Original Assignee: UTC Fuel Cells, LLC
• Inventors: Resto, Javier, Morrow, Aaron W., Erlich, Grant M.
• Primary Examiner(s): Ryan, Patrick
• Assistant Examiner(s): Mercado, Julian
• Application Number:
  US10/141,612
• Publication Number:
  US 20030211379A1
• Time in Patent Office: 804 Days
• Field of Search: 429/34, 429/37, 429/39
• US Class Current: 429/434
• CPC Class Codes: H01M 8/0213 Gas-impermeable carbon-containing materials
• CPC Class Codes: H01M 8/0247 characterised by the form characterised by a channel configuration H01M8/0258
• CPC Class Codes: H01M 8/0267 having heating or cooling means, e.g. heaters or coolant flow channels
• CPC Class Codes: H01M 8/0271 Sealing or supporting means around electrodes, matrices or membranes
• CPC Class Codes: H01M 8/0276 Sealing means characterised by their form H01M8/0273 takes precedence
• CPC Class Codes: H01M 8/04067 Heat exchange or temperature measuring elements, thermal insulation, e.g. heat pipes, heat pumps, fins
• CPC Class Codes: H01M 8/241 with solid or matrix-supported electrolytes
• CPC Class Codes: H01M 8/248 Means for compression of the fuel cell stacks
• CPC Class Codes: H01M 8/2483 characterised by internal manifolds
• CPC Class Codes: Y02E 60/50 Fuel cells

Abstract

The invention is a fuel cell stack having an improved pressure plate and current collector. The fuel cell stack includes a plurality of fuel cell component plates stacked adjacent each other to form a reaction portion of the fuel cell stack. A current collector is secured adjacent a first end of the stack of fuel cell component plates and a pressure plate is secured adjacent to the current collector. The current collector is made from a non-porous, electrically conductive graphite material and includes at least one conductive stud secured to the collector. The pressure plate is made of an electrically non-conductive, non-metallic, fiber reinforced composite material, so that the current collector and pressure plate are light, compact and have a low thermal capacity.

Claims

1. A fuel cell stack for producing electricity from reducing fluid and process oxidant reactant streams, comprising:

a. a plurality of fuel cell component plates stacked adjacent each other to form a reaction portion of the fuel cell stack, the plurality of fuel cell component plates including a first end cell component plate at a first end of the stack of fuel cell component plates, and a second end cell component plate at an opposed second end of the stack of fuel cell component plates;

b. a current collector secured adjacent to an end cell component plate, wherein the current collector is made from non-porous, electrically conductive graphite material, and wherein the current collector includes at least one conductive stud secured to the collector and extending away from the current collector in a direction away from the end cell component plate; and

,

c. a first pressure plate secured adjacent the current collector and overlying the end cell component plate, wherein the first pressure plate is made of an electrically non-conductive, non-metallic, fiber reinforced composite material, and wherein the first pressure plate defines a plurality of tie rod protrusions, each tie rod protrusion defining a throughbore dimensioned to receive a tie rod that passes through a second pressure plate to apply a compressive force to the fuel cell stack of between 50 and 100 pounds per square inch.

2. The fuel cell stack of claim 1, further comprising a thermal insulator secured between the current collector and the first pressure plate.

3. The fuel cell stack of claim 1, wherein the current collector has a conductivity equal to or greater than 25 siemens per centimeter.

4. The fuel cell stack of claim 1, wherein the first pressure plate includes a gas seal extending between a periphery of the pressure plate to the end cell component plate.

5. The fuel cell stack of claim 1, further comprising a plurality of conductive studs secured to the current collector, wherein the plurality of conductive studs extend through the first pressure plate.

6. The fuel cell stack of claim 1, wherein the current collector is dimensioned to fit within a cavity defined within the first pressure plate so that the current collector is flush mounted within the cavity of the pressure plate.

7. The fuel cell stack of claim 1, wherein the current collector includes a metal layer secured to a layer of electrically conductive graphite material, the current collector being secured so that the metal layer is positioned between the layer of the electrically conductive graphite material and the electrically non-conductive, non-metallic, fiber reinforced first pressure plate.

8. The fuel cell stack of claim 1, wherein the first pressure plate defines at least one coolant header integral with the pressure plate for directing flow of a cooling fluid through the pressure plate and into the fuel cell stack.

9. A fuel cell stack for producing electricity from reducing fluid and process oxidant reactant streams, comprising:

a. a plurality of fuel cell component plates stacked adjacent each other to form a reaction portion of the fuel cell stack, the plurality of fuel cell component plates including a first end cell component plate at a first end of the stack of fuel cell component plates, and a second end cell component plate at an opposed second end of the stack of fuel cell component plates;

b. a first current collector secured adjacent the first end cell component plate, and a second current collector secured adjacent the second end cell component plate, wherein the first and second current collectors are made from non-porous, electrically conductive graphite material, and wherein the first current collector includes at least one conductive stud secured to the first current collector and extending away from the first current collector in a direction away from the first end cell component plate and the second current collector includes at least one conductive stud secured to the second current collector and extending away from the second current collector in a direction away from the second end cell component plate; and

,

c. a first pressure plate secured adjacent the first current collector and overlying the first end cell component plate, and a second pressure plate secured adjacent the second current collector and overlying the second end cell component plate, wherein the first and second pressure plates are made of an electrically non-conductive, non-metallic, fiber reinforced composite material, and wherein the first and second pressure plates each define a plurality of tie rod protrusions, each tie rod protrusion defining a throughbore dimensioned to receive a tie rod that passes between the throughbores of the first and second pressure plates to apply a compressive force to the fuel cell stack of between 50 and 100 pounds per square inch.

10. The fuel cell stack of claim 9, wherein the fuel cell stack further comprises a first thermal insulator secured between the first current collector and the first pressure plate, and a second thermal insulator secured between the second current collector and the second pressure plate.

11. The fuel cell stack of claim 9, wherein the first and second current collectors each have a conductivity equal to or greater than 25 siemens per centimeter, the first pressure plate includes a first gas seal extending between a periphery of the first pressure plate to the first end cell component plate, and the second pressure plate includes a second gas seal extending between a periphery of the second pressure plate to the second end cell component plate.

12. The fuel cell stack of claim 9, wherein the first current collector is dimensioned to fit within a cavity defined within the first pressure plate so that the first current collector is flush mounted within the cavity of the first pressure plate, and the second current collector is dimensioned to fit within a cavity defined within the second pressure plate so that the second current collector is flush mounted within the cavity of the second pressure plate.

13. The fuel cell stack of claim 9, wherein the first pressure plate defines at least one coolant header integral with the first pressure plate for directing flow of a cooling fluid through the pressure plate and through the fuel cell stack, and the second pressure plate defines at least one coolant header integral with the second pressure plate for directing flow of the cooling fluid through the second pressure plate and through the fuel cell stack.